Glass fibers are typically treated after forming with a sizing composition that can impart desired properties. As used herein the term “size”, “sized”, “sizing” and “sizing composition” means a coating composition that can be applied to the glass fibers after formation of the fibers. After their formation and treatment, the sized glass fibers can be gathered into bundles or strands comprising a plurality of individual fibers. The strands may be wound into a spool or “forming package.” The forming packages can be dried to remove moisture from the fibers.
A sizing composition can serve several functions. It can function as a lubricant and binding agent and can protect fibers from abrasion with each other.
A sizing composition can also improve the performance of fibers during further processing such as when used to reinforce thermoplastic resins. For example, thermoplastic resins can be reinforced with sized glass fibers to strengthen and stiffen the resulting composite material. The sizing on the glass fibers can improve compatibility between the inorganic surface of glass fibers and an organic thermoplastic resin.
Many glass fiber reinforced thermoplastic resins are used in the automotive industry. For example, glass fiber reinforced polyamide resins are used to fabricate containers for various automotive fluids such as oil pans and radiator parts that encapsulate the core of the radiator. The combination of high temperatures and exposure to aqueous organic solvent mixtures such as ethylene glycol and water can decrease the strength of polyamide resins used in automotive applications. Specifically, a polyamide resin can be weakened by hydrolysis of the amide bonds of the polyamide.
Thus, it would be advantageous to provide a sizing composition that can improve the hydrolysis resistance of a glass fiber reinforced thermoplastic resin. It would also be advantageous to provide a sizing composition that can improve or maintain the strength of a glass fiber reinforced thermoplastic resin when lubricated with a fatty acid metal salt.